High-frequency low-loss composite magnetic core material and preparation method and application thereof

Abstract

The application discloses a high-frequency low-loss composite magnetic core material and a preparation method and application thereof, and particularly relates to the technical field of soft magnetic composite materials; the composite magnetic core material is prepared from a base component and a doping component through pre-burning, pressing and sintering; the base component comprises Fe2O3, MnO and ZnO; the doping component comprises BiFeO3, SrTiO3, WO3, Co2O3, CaCO3, Nb2O5 and V2O5; the application optimizes the synergistic effect of the base component and the doping component, suppresses the loss, improves the initial magnetic permeability, realizes the balance between the high frequency and the low loss and the high magnetic permeability, and meets the high-performance requirement of high-frequency power electronic devices on the magnetic core material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soft magnetic composite materials, and particularly relates to a high-frequency low-loss composite magnetic core material and a preparation method and application thereof. BACKGROUND

[0002] Soft magnetic composite materials, especially manganese-zinc ferrite series materials, are widely used in high-frequency power electronic devices (such as transformers, inductors, etc.) due to their high magnetic permeability and low loss characteristics. However, with the development of power electronic devices towards high frequency, miniaturization and high efficiency, traditional manganese-zinc ferrite materials have exposed significant technical bottlenecks under high frequency (such as above 100 kHz) working conditions.

[0003] Firstly, under high frequency environment, the eddy current loss and dielectric polarization loss of the material increase sharply. This is because the traditional material has high conductivity at the grain boundary, which forms a vortex path between the grains in the alternating magnetic field; at the same time, the material has a large dielectric constant, which aggravates the polarization loss under high frequency electric field. These problems not only reduce the efficiency of the device, but also cause the magnetic core to heat up, affecting the reliability and life of the device.

[0004] Currently, researchers try to improve the high-frequency performance by doping modification and process optimization, but there are still deficiencies: 1. Single doping or simple compounding is difficult to form a continuous high-resistance layer at the grain boundary, and the dielectric constant is not enough; 2. It is difficult to balance low loss and high magnetic permeability; 3. The traditional sintering process cannot accurately control the grain boundary structure and component distribution, affecting the consistency of material performance, etc. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a new composite magnetic core material, which optimizes the grain boundary characteristics through the synergistic effect of multiple components, and realizes the efficient balance of high frequency, low loss and high magnetic permeability by combining with the fine preparation process.

[0006] In order to achieve the above purpose, the present application discloses the following technical scheme:

[0007] In the first aspect, the present application provides a high-frequency low-loss composite magnetic core material, which is formed by pre-burning, pressing and sintering of a base component and a doping component;

[0008] The base component includes the following components by 100% moles of the base component:

[0009] Fe2O3 51-52mol%;

[0010] MnO 38-39mol%;

[0011] ZnO 10-11mol%;

[0012] The doping component includes the following components in terms of the total mass percentage of the base component:

[0013]

[0014] Preferably, the base component includes the following components in terms of 100% moles of the base component:

[0015] Fe2O3 51.65 mol%;

[0016] MnO 38.21 mol%;

[0017] ZnO 10.14 mol%.

[0018] In a second aspect, the present application provides a preparation method of the high-frequency low-loss composite magnetic core material of the first aspect, the preparation method comprising the following steps:

[0019] Step 1. A certain amount of Fe2O3, MnO and ZnO base component is weighed and wet ball milled, and the obtained slurry is sieved and dried after sieving to a water content of ≤0.1%, obtaining a pretreated powder;

[0020] Step 2. The pretreated powder is pre-fired at 850-900°C, and after being heated from room temperature to the pre-firing temperature, it is kept for 2-4h, and then cooled to obtain a manganese-zinc-iron oxide base material, wherein the entire pre-firing is carried out in an air atmosphere;

[0021] Step 3. The doping component is weighed, mixed with the manganese-zinc-iron oxide base material, and then wet ball milled, and after ball milling, PVA binder is added and mixed uniformly, wherein the addition amount of PVA binder is 0.5-0.8% of the total mass of the slurry, and the uniformly mixed slurry is spray granulated to obtain a granulated material;

[0022] Step 4. The granulated material is pressed into a green body, and the green body is sintered, and the sintering process is first heated from room temperature to 450-500°C at a heating rate of 0.4-0.5°C / min, and then heated to 1300-1400°C at a rate of 4-5°C / min, and then kept for 4-5h in a 92v / v% N2 / 8v / v% O2 mixed gas atmosphere, and then cooled to room temperature to obtain a high-frequency low-loss composite magnetic core material.

[0023] Preferably, the ball milling in step 1 is to place the Fe2O3, MnO and ZnO base component in a ball mill, add steel grinding balls at a ball-to-material ratio of 5:1, add deionized water at a solid-to-liquid ratio of 1:1.5, and ball mill at a speed of 500r / min for 3-4h.

[0024] Preferably, the slurry is sieved through a 200-mesh sieve.

[0025] Preferably, the step 2 places the pretreated powder into a smelting instrument, and the temperature is raised from room temperature to 270-300 DEG C at a rate of 2-3 DEG C / min, and then the temperature is kept at 270-300 DEG C for 1 h to completely remove the water adsorbed on the surface of the powder, and then the temperature is raised from 270-300 DEG C to 850-900 DEG C for pre-sintering at a rate of 10-15 DEG C / min.

[0026] Preferably, the step 3 places the doping component and the manganese-zinc ferrite body into a ball mill, and steel balls are added at a ball-to-material ratio of 5:1, deionized water is added at a solid-to-liquid ratio of 1:1.5, the ball milling speed is 500 r / min, and the ball milling is performed until the slurry particle size D90 is 500-700 nm.

[0027] The PVA binder is a PVA binder with a concentration of 8-10%.

[0028] Preferably, the step 3 is performed by setting the spray granulation parameters as follows: the inlet temperature is 180-220 DEG C, the outlet temperature is 90-110 DEG C, and the atomization pressure is 0.3-0.8 MPa.

[0029] Preferably, the density of the green body formed by the step 4 is controlled to be 2.95-3.10 g / cm 3 .

[0030] In a third aspect, the application provides a use of the high-frequency low-loss composite magnetic core material in the preparation of high-frequency power electronic components.

[0031] In the application, bismuth ferrite (BiFeO3) is introduced, which has a rhombohedric perovskite structure and a space group R3c, and is significantly different from the crystal structure of the manganese-zinc ferrite with a spinel structure, so that the bismuth ferrite cannot be solid-solved in the main phase and is preferentially precipitated at the grain boundaries during sintering to form an insulating barrier, thereby reducing the high-frequency eddy current loss, and the weak ferromagnetism of the bismuth ferrite can partially compensate for the dilution effect of the non-magnetic additive on the magnetic permeability.

[0032] In the application, strontium titanate (SrTiO3) is introduced, which has a perovskite structure and a space group Pm3m, and is significantly different from the crystal structure of the manganese-zinc ferrite with a spinel structure, so that the strontium titanate cannot be solid-solved in the manganese-zinc ferrite lattice and can only be precipitated at the grain boundaries, and the strontium titanate has a high resistivity to form a continuous high-resistance layer at the grain boundaries to block the conduction path between the grains, which synergistically enhances the effect of the tungsten trioxide at the grain boundaries to significantly inhibit the high-frequency eddy current loss, and the low dielectric constant of the strontium titanate can effectively reduce the dielectric polarization loss at high frequencies to avoid heating of the magnetic core.

[0033] As a non-magnetic phase, the excessive addition of strontium titanate can dilute the concentration of magnetic ions, cause non-magnetic dilution effect, and reduce the saturation magnetization and initial permeability.

[0034] The crystal structure of tungsten trioxide (WO3) is monoclinic or tetragonal phase, and the space group is P21 / n or P4 / nmm, which is significantly different from the space group of spinel structure manganese zinc ferrite, and is difficult to be solid-solved into the main crystal lattice, and tends to be precipitated at the grain boundary, as a high resistivity substance, tungsten trioxide can effectively block the conductive path at the grain boundary and inhibit high-frequency eddy current loss.

[0035] Synergistic effect: when tungsten trioxide, strontium titanate and bismuth ferrite are matched, the former reduces the grain boundary loss, and the latter compensates for the permeability, achieving the balance of high frequency and low loss and high permeability.

[0036] Advantages of the present application:

[0037] 1. The present application introduces BiFeO3, SrTiO3 and WO3 and other doping components into manganese zinc ferrite, forms a high resistivity insulating layer at the grain boundary of manganese zinc ferrite, cooperatively blocks the intergranular conductive path, and inhibits high-frequency eddy current loss, thereby significantly reducing the total power loss of the material under high-frequency application.

[0038] 2. The synergistic effect of the optimized base component and the doping component is optimized, the loss is inhibited, the initial permeability is improved, the balance of high frequency and low loss and high permeability is achieved, and the high performance demand of high-frequency power electronic devices for magnetic core materials is met. DETAILED DESCRIPTION

[0039] The present application will be further described and illustrated in detail below in combination with specific embodiments. Those skilled in the art will be able to implement the present application based on these descriptions. In addition, the embodiments of the present application involved in the following description are generally only a part of the embodiments of the present application, not all the embodiments.

[0040] Therefore, based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor shall belong to the scope of protection of the present application. Unless otherwise specified, the raw materials used in the embodiments of the present application are commercially available or can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present application are methods mastered by those skilled in the art.

[0041] In the present application:

[0042] The raw materials used in the embodiments are commercially available.

[0043] Preparation of the composite magnetic core material

[0044] Step 1. Accurately weigh the base components of Fe2O3, MnO and ZnO according to the mole percentage in Table 1, and place them in a ball mill tank. Add steel grinding balls at a ball-to-material ratio of 5:1, and add deionized water to a solid-to-liquid ratio of 1:1.5. Mill at a speed of 500 r / min, and obtain a slurry with a particle size D90 of 500-700 nm. At this time, add 10% PVA binder to the slurry, and mix uniformly. The amount of PVA binder added is 0.8% of the total mass of the slurry. Spray granulation is then performed, with the inlet temperature set to 200°C, the outlet temperature set to 100°C, and the atomization pressure set to 0.8 MPa. The granulated material is obtained.

[0045] Step 2. Place the pretreated powder in an electric smelting crucible, and heat from room temperature to 285°C at a rate of 3°C / min. After reaching 285°C, maintain the temperature for 1 h. Then, heat from 285°C to 900°C at a rate of 10°C / min, and maintain the temperature for 2-4 h after reaching the pre-sintering temperature. After pre-sintering, cool to obtain the manganese-zinc-iron oxide base material. The entire pre-sintering process is carried out in an air atmosphere.

[0046] Step 3. Accurately weigh the doping components according to the mass percentage in Table 1, and place the doping components and the manganese-zinc-iron oxide base material in a ball mill tank. Add steel grinding balls at a ball-to-material ratio of 5:1, and add deionized water to a solid-to-liquid ratio of 1:1.5. Mill at a speed of 500 r / min until the particle size D90 of the slurry is 500-700 nm. At this time, add 10% PVA binder to the slurry, and mix uniformly. The amount of PVA binder added is 0.8% of the total mass of the slurry. Spray granulation is then performed, with the inlet temperature set to 200°C, the outlet temperature set to 100°C, and the atomization pressure set to 0.8 MPa. The granulated material is obtained.

[0047] Step 4. Use a double-action press to press the granulated material into a ring-shaped blank with an outer diameter of 18 mm, an inner diameter of 10 mm, and a height of 6 mm. The density of the blank is controlled to be 2.95-3.10 g / cm 3 Place the blank in a sintering furnace for sintering. First, heat from room temperature to 500°C at a rate of 0.5°C / min in an air atmosphere, and maintain the temperature for 1 h. Then, rapidly heat to 1340°C at a rate of 4.5°C / min, and maintain the temperature for 4-5 h in a mixed gas atmosphere of 92 v / v% N2 and 8 v / v% O2. After sintering is completed, cool to room temperature to obtain the high-frequency low-loss composite magnetic core material.

[0048] Table 1 Raw material composition

[0049]

[0050] To verify the effect of the key components in the doping components and the influence of the key components on the performance of the composite magnetic core material, the doping components are adjusted by default and in amount based on the formulation of Example 2, as follows:

[0051] Comparative Example 1: BiFeO3 is absent, the rest is unchanged;

[0052] Comparative Example 2: SrTiO3 is absent, the rest is unchanged;

[0053] Comparative Example 3: WO3 is absent, the rest is unchanged;

[0054] Comparative Example 4: BiFeO3 is increased to 0.2wt%, the rest is unchanged;

[0055] Comparative Example 5: SrTiO3 is increased to 0.01wt%, the rest is unchanged;

[0056] Comparative Example 6: WO3 is increased to 0.02wt%, the rest is unchanged.

[0057] Performance test

[0058] The composite magnetic core materials prepared from Examples 1-3 and Comparative Examples 1-6 were tested for performance, with 3 repeats for each group of samples and the average value taken;

[0059] Initial permeability test was conducted at 25℃, 10kHz using Japanese IWATSU Iwasaki B-H tester SY-8219;

[0060] High frequency power loss test was conducted at 100℃, 100kHz, 200mT test conditions;

[0061] The specific test results are shown in Table 2.

[0062] Table 2 Performance test results of Examples 1-3 and Comparative Examples 1-6

[0063] Group Initial permeability, 10 kHz High frequency power loss / kW m -3 ]] Example 1 3704 242 Example 2 4183 239 Example 3 3936 244 Comparative Example 1 3117 397 Comparative Example 2 3341 427 Comparative Example 3 3256 431 Comparative Example 4 3629 343 Comparative Example 5 2914 324 Comparative Example 6 2902 311 Current market level 3500 420

[0064] Result analysis:

[0065] The initial permeability of Comparative Example 1 was significantly lower than that of Example 2, and the high frequency power loss was greatly increased. This shows that BiFeO3 forms an insulating barrier by precipitating grain boundaries, effectively suppressing eddy current loss, while its weak ferromagnetism compensates for the dilution effect of non-magnetic additives, thereby improving the permeability.

[0066] The high frequency power losses of Comparative Examples 2 and 3 reached 427kW·m -3 and 431kW·m -3 , respectively, which were much higher than that of Example 2. This shows that the high resistivity of SrTiO3 and the grain boundary blocking effect of WO3 synergistically reduce the high frequency eddy current loss, while the low dielectric constant of SrTiO3 reduces the dielectric polarization loss.

[0067] The magnetic permeability and loss of Comparative Example 4 are both worse than those of Example 2, indicating that excessive BiFeO3 leads to excessive thickening of the grain boundary, affecting the magnetic domain movement. The magnetic permeability of Comparative Example 5 and Comparative Example 6 is reduced to 2914 and 2902, respectively, indicating that excessive non-magnetic phase dilutes the concentration of magnetic ions, verifying the necessity of limiting the doping amount range in the present application.

[0068] Example 2 has the best comprehensive performance, with an initial magnetic permeability of 4183 and a high-frequency power loss of only 239 kW·m -3 , which is significantly better than the existing level on the market. This shows that the synergistic optimization of the matrix components (Fe2O351.65 mol%, MnO38.21 mol%, ZnO 10.14 mol%) and the doping components provided by the present application, combined with the staged temperature control sintering process, achieves a balance between grain boundary regulation and magnetic performance.

[0069] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above is only a specific embodiment of the present application and is not intended to limit the protection scope of the embodiments of the present application. Any modification, equivalent replacement, improvement, etc. made on the basis of the technical solutions of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A high frequency low loss composite magnetic core material, characterized by, The composite magnetic core material is prepared by pre-sintering, pressing and sintering of a base component and a doping component; The base component comprises the following components in terms of 100% moles of the base component: Fe2O3 51.65 mol%; MnO 38.21 mol%; ZnO 10.14 mol%; The doping component comprises the following components in terms of the total mass of the base component: BiFeO3 0.015-0.025 wt%; SrTiO3 0.002-0.005 wt%; WO3 0.006-0.010 wt%; Co2O3 0.1-0.5 wt%; CaCO3 0.001-0.004 wt%; Nb2O5 0.001-0.002 wt%; V2O5 0.01-0.05 wt%.

2. The method of producing a high-frequency low-loss composite core material according to claim 1, characterized by, The preparation method comprises the following steps: Step 1. A certain amount of Fe2O3, MnO and ZnO base component is weighed and wet ball milled to obtain a slurry, which is sieved and dried to a water content of ≤0.1% to obtain a pretreated powder; Step 2. The pretreated powder is pre-sintered at 850-900℃, and after being heated from room temperature to the pre-sintering temperature, it is kept for 2-4h, and then cooled to obtain a manganese-zinc-iron oxide base material, wherein the entire pre-sintering process is carried out in an air atmosphere; Step 3. The doping component is weighed and mixed with the manganese-zinc-iron oxide base material, and then wet ball milled, and after ball milling, PVA binder is added and mixed uniformly, wherein the addition amount of PVA binder is 0.5-0.8% of the total mass of the slurry, and the uniformly mixed slurry is spray granulated to obtain granulated material; Step 4. The granulated material is pressed into a green body, and the green body is sintered, and in the sintering process, the temperature is first raised from room temperature to 450-500℃ at a heating rate of 0.4-0.5℃ / min, and then kept for 1h, and then heated to 1300-1400℃ at a rate of 4-5℃ / min, and then kept for 4-5h in a 92v / v% N2 / 8v / v% O2 mixed gas atmosphere, and then cooled to room temperature to obtain a high-frequency low-loss composite magnetic core material.

3. The preparation method according to claim 2, characterized in that, In step 1, the Fe2O3, MnO and ZnO base component is placed in a ball mill, steel balls are added at a ball-to-material ratio of 5:1, deionized water is added at a solid-to-liquid ratio of 1:1.5, the ball milling speed is 500r / min, and the ball milling is carried out for 3-4h.

4. The production method according to claim 2, characterized by, The slurry is sieved through a 200 mesh sieve.

5. The preparation method according to claim 2, characterized in that, In step 2, the pretreated powder is placed in a smelting instrument, heated from room temperature to 270-300℃ at a heating rate of 2-3℃ / min, kept for 1h after reaching 270-300℃, and then pre-sintered by heating from 270-300℃ to 850-900℃ at a heating rate of 10-15℃ / min.

6. The preparation method according to claim 2, characterized in that, In step 3, the doping component and the manganese-zinc-iron oxide base material are placed in a ball mill, steel balls are added at a ball-to-material ratio of 5:1, deionized water is added at a solid-to-liquid ratio of 1:1.5, the ball milling speed is 500r / min, and the ball milling is carried out until the slurry particle size D90 is 500-700nm; The PVA binder is a PVA binder with a concentration of 8-10%.

7. The preparation method according to claim 2, characterized in that, In step 3, the spray granulation parameters are set as follows: inlet temperature 180-220 DEG C, outlet temperature 90-110 DEG C, and atomization pressure 0.3-0.8 MPa.

8. The preparation method according to claim 2, characterized in that, The density of the compression-molded compact of Step 4 is controlled to be 2.95 to 3.10 g / cm 3 .

9. Use of the high-frequency low-loss composite magnetic core material of claim 1 in the preparation of high-frequency power electronic components.

Images